A rolling boot comprises a first fastening region for fastening the boot to a joint casing, a second fastening region for fastening the boot to a shaft, and a fold region between the first and the second fastening region with a first fold near to the first fastening region and a second fold near to the second fastening region. Further disclosed is a plunge joint with a rolling boot in accordance with the present disclosure, as well as a joint arrangement with at least one rolling boot, and a shaft.
Rolling boots in accordance with the present disclosure may be used especially for plunge joints, for example in the form of a ball-and-socket joint or trilobe joint, and especially for constant velocity joints, all of them, e.g., in an embodiment as a plunge joint. Rolling boots are also referred to as diaphragm boots; however, the term rolling boot will be used herein.
Rolling boots, in contrast to convolute boots, only have a fold region with two folds, one of them having a convex shape, and the other having a concave shape. Said two folds show a straight through their peak region that is more or less parallel to a main axis of the boot, if viewed in a longitudinal section, and that divides the folds approximately in half. In convolute boots, to the contrary, such a straight is more or less perpendicular to such a main axis. The present disclosure only relates to such rolling boots, and not to convolute boots.
Rolling boots are mounted on joint casings by way of a binder element, also called a tensioning element, being also used to fix said boots on a shaft in the second fastening region which is oppositely arranged from the first fastening region in the boot in accordance with the present disclosure. Such boots are usually made of a thermoplastic elastomer material or mixtures of thermoplastic elastomer materials, for example based on polyurethane (TPU), polyamide (TPA), polyolefins (TPO), polyester (TPEE), thermoplastic elastomer vulcanisate (TPV), or a thermoplastic poly-ether-ester-elastomer (TPC-ET). The material or mixtures of materials of the boots in accordance with the present disclosure may be made of or may further comprise other materials, especially additives like diffusion-promoting admixtures or any other additives a person skilled in the art will be aware of in view of the use of the boot in question, especially in view of the demands of the automotive industry if the boots are used for automotives. However, the boots in accordance with the present disclosure may also be made of usual rubber-elastic materials.
WO 2009/155955 A1 discloses a rolling boot for mounting on a joint casing. If the joint will be a trilobe joint, it will be necessary to use in addition an adapter to fasten said rolling boot to the joint casing. Said rolling boot disclosed in WO 2009/155955 A1 shows a certain design for a first fold with an angle α, measured between an outer base surface of a transition region and an outer side of a first fold flank of said first fold, being in a range between 90° to 140°. The first fold has a very special design, especially of the fold peak region having the shape of a sharp nose. The object to be solved by said rolling boot is to provide for a rolling boot withstanding grease pressure acting on the rolling boot during use. Said rolling boot is of compact design and has a reduced inside diameter, thereby reducing the grease pressure acting on the rolling boot when it is exposed to centrifugal forces.
However, due to said special design, the rolling boot disclosed in WO 2009/155955 A1 has a decreased form stability in use, especially at higher revolutions per minute. Due to said decreased form stability, it is necessary to provide for retention rings for hindering any disassembly of a joint arrangement, and is further necessary to provide for means in a joint arrangement, for example shaft spring means as disclosed in WO 2009/066128 A 1, to urge the shaft toward a predetermined position with respect to the joint inner parts, the latter also called male member of a joint. In addition, WO 2009/066128 A1 discloses first actual fixing means fixing the male member on the shaft in the axial direction with respect to a central axis.
Accordingly, disclosed herein is a rolling boot as well as a plunge joint and a joint arrangement comprising such a rolling boot showing increased form stability compared to rolling boots known from the state of the art.
For example, a boot as defined above comprises further, between the first fastening region and the first fold, a first transition region comprising a first flange neighbouring, e.g., directly arranged at, the first fastening region with a bottom, wherein a ratio between a first minimal diameter D1, defined by the bottom of the first flange of the first transition region, and a second maximal diameter D2, defined by the first fold, both if viewed in a longitudinal section along the main axis of the boot, is between approximately 1:1.01 to approximately 1:1.25, e.g., to 1:1.18, further, e.g., between approximately 1:1.02 to approximately 1.12, and yet further, e.g., between approximately 1:1.03 to approximately 1:1.09. Due to the radial symmetric embodiment of the rolling boot of the present invention, it will be seen that a bottom of the first flange of the first transition region may also be defined as the top surface of a rib being arranged at least in part at the inner circumference of the boot. From this it is clear that the diameter D1 is the distance between the bottom of the first flange measured inside the boot in accordance with the present invention. The second maximal diameter D2, as defined by the first fold, is defined by the outside maximum of the first fold defined in relation to the main axis of the boot. In a mathematical sense, one may define said maximum of a first fold being a kind of a turning point of said first fold, being the outside maximum turning point with respect to the main axis of the boot. Both diameters are defined in view of a boot in an unassembled condition.
In a further embodiment the first transition region provides for at least in part with respect to the circumference of the boot an angle α in a region between approximately 30° to 89.8°, e.g., in a region between approximately 56° to approximately 86°, further, e.g., in a region between approximately 60° to approximately 82°, and yet further, e.g., in a region between approximately 62° to approximately 80°.
As used herein, the term “approximately” is to be understood in that values so referred to are not limited to the exact value, but rather that also small deviations from the referred-to value shall be encompassed. Especially, deviations of +/−5%, or more especially, +/−2%, and yet further +/−1%, are within the scope of the term “approximately” in reference to the value in question. It has to be noted that the upper limit of 89.8° is not defined as being approximately 89.8°, meaning that the upper value 89.8° is an exact value defining the end of the range defined.
The meaning of the term “ . . . at least in part with respect to the circumference of the boot an angle α . . . is provided for . . . ” is that it is also possible that the rolling boot in accordance with the present invention may have protuberances on the outer circumference of the boot in the region of the first transition region, wherein such protuberances may act for encompassing rollers of a plunge joint. If such protuberances are arranged around the circumference of the boot in question in the first transition region and have a conical shape, thus presenting the second flange, then in the part of the first transition region between said protuberances, an angle α will be measured.
The first flange of said first transition region is, e.g., arranged at an essentially right angle with respect to an inner surface of the first fastening region, e.g., at a right angle. However, also other angles are possible, if the joint outer part on which the boot is to be mounted may have a joint front edge being not arranged in an essentially right angle. The first flange of the boot in accordance with the present invention will, e.g., be in direct contact with the surface of the front edge of the joint outer part, e.g., at least 70% of said inner surface will be in direct contact with the surface of the front edge of the joint outer part.
The rolling boot disclosed herein may especially be used for ball-and-socket plunge joints or plunge joints with a triblobe inner contour. Thus, the rolling boot may be used in addition to an adapter for adaptation on a triblobe embodied joint casing. However, the inner contour of the rolling boot could be already adapted to the trilobe outer contour of a joint casing in case of a trilobe plunge joint, especially a trilobe constant velocity joint, in order to avoid use of any adapter.
In the context of the present disclosure, the term “first transition region” is to be understood as a region neighbouring the first fastening region, e.g., neighbouring immediately the first fastening region. It starts with the first flange, being arranged e.g., at an essentially right angle with respect to an inner surface of said first fastening region. If referred to a joint casing, said first flange may be described as encompassing in part the front of the joint casing directed towards the fold region of the rolling boot.
The term “arranged at an essentially right angle” in the context of the present disclosure means that although it is preferred that the angle between the outer surface of said first flange and an inner surface, or a straight prolongating said inner surface, of the first fastening region, is 90°, that also deviations from the are encompassed. For example, deviations of said right angle of +/−5%, further preferred +/−2%, are within the meaning of said term.
The end region of the first transition region may be defined by the second flange of the boot having the conical shape, if viewed in the longitudinal section along the main axis of the boot, neighbouring, e.g., immediately neighbouring, the first curved part of the first fold of the fold region of the claimed rolling boot.
The angle α is defined by said outer surface of said first flange of the claimed boot being arranged at an essentially right angle with respect to said inner surface of said first fastening region, and an outer surface of said second flange having a conical shape. From said first transition region, a cylindrical part, arranged between the first flange and the second flange, may also be comprised. In case such a cylindrical part between the first and the second flange of the first transition region is present, said angle α is measured between a parallel of said outer surface of said first flange, going through the starting point of the second flange with the conical shape.
An advantage of the presently disclosed boot is that it provides for an increased form stability, including if no outer or inner reinforcing ribs are present. However, outer and/or inner reinforcing ribs may be present between the first fold and the transition region, or within the first fold, or between the first and the second fold within the boot, respectively. The reinforcing ribs may be arranged, for example, alternatively within the boot and outside the boot. It is also possible that only outer reinforcing ribs, or only inner reinforcing ribs, are present. For example, 6, 8, 10, or 12 outer and/or inner reinforcing ribs may be present.
Further due to said increased form stability, a disassembly of the inner parts of a joint is hindered, i.e., due to the high retention force imparted by the boot of the present disclosure. Thus, the risk of disassembly of the inner parts of a joint through bending or plunging at high angles will be diminished.
Further, due to the high form stability imparting high retention forces, the rolling boot in accordance with the present disclosure may be in a position to provide for an axial centering of a shaft in a plunge joint, so that retention rings or spring means or other means known from the state of the art may be omitted. In that respect, and compared to convolute boots, also the decreased air volume within the boot support said axial centering. The ratio of a grease amount to be included in a joint arrangement with the rolling boot in accordance with the present disclosure versus a residual air volume within the boot can be used to optimize the retention behaviour of such a joint arrangement.
In a further embodiment, a radius rM, derived from diameter D1, is essentially identical to a smallest radius rL of the claimed rolling boot, if said rolling boot will have a trilobe inner contour in order to be fixed on a trilobe joint casing without the need of any adapter, or the smallest diameter provided for by such a trilobe adapter, if the rolling boot will not have a trilobe inner contour in the first fastening region.
If the ratio between diameters D1 and D2 will be within the range as claimed, advantageously the production of the rolling boot in question will be simplified, because the geometry of the claimed boot will show a limited undercut, especially if the angle α will be within approximately 60° to approximately 82°. Further, a maximum for the retention force will be provided for with a ratio between diameters D1 and D2 as defined before.
In accordance with a further embodiment, between the second fold and the second fastening region a second transition region with a conical part with decreasing diameter d towards the second fastening region is comprised. The diameter d referring to the conical part of the second transition region is defined by opposing inner surfaces of the conical part. The conical part of the second transition region is defined as a part of the second transition region without any curved parts, and, further, having, e.g., an essentially steadily decreasing diameter, starting from the fold region towards the second fastening region. In an embodiment, the second transition region only comprises said conical part.
By the provision of said second transition region, the boot will be in a position to brace against the shaft, without creating negative effects such as knocking within the joint agreement.
In a further embodiment, the boot comprises a transition from the second transition region to the second fastening region, the transition being essentially continuous. “Essentially continuous” as used herein means that, without any step or any stage, the second fastening region is attached to the second transition region. Especially, said transition is stage- or stepless. However, a kind of a bead or rib or accumulation of material may be formed at the transition between the second transition region and the second fastening region, e.g., having a smoothed outer contour, for example a curved contour. All of the aforesaid refers to the inner side of the presently-disclosed boot. The transition, thus, is located on the inside surface of the material of the boot in the region where the second fastening region is attached to the second transition region. For example, no protrusion, accumulation of material of each kind, and so on, are present at the transition, so that said transition is in fact stage- or stepless. The aforesaid definition of the transition does not exclude that the thickness of the material of the boot in the second fastening region may be greater than the thickness of the material of the boot in the second transition region.
In a further embodiment, a thickness of the boot material varies from the first transition region to the second transition region. Thus, also the thickness of the boot material within the first transition and/or the second transition region itself may vary. For example, the thickness varies in a region between approximately 0.5 mm to approximately 3 mm, preferred, e.g., in a region between approximately 0.8 mm to approximately 2 mm.
In a further embodiment, the thickness of the boot material decreases within the first fastening region. Further, e.g., the thickness of the boot material varies within said second fold. Yet further, e.g., a minimum of the thickness of the boot material lies within said second fold.
The variation of the thickness of the boot material, e.g., in the regions as defined before, allows a fine tuning of the retention force, and, thus, the form stability of the boot claimed. The boot in use provides for two different ranges of operation that may be measured and visualized in a force/path diagram. For example, a first range A of operation exists, where in use the forces, especially the axial force, will only increase slightly, whereas a second range of operation B immediately neighbouring said first range of operation will be present in which the forces, especially the axial force, will increase drastically, practically ad infinitum. Due to said second range of operation B, the boot in accordance with the present disclosure will have the ability for axial centering of shafts in joints, especially plunge joints. The variation of the thickness of the boot material, especially in the regions as mentioned before, will allow also a fine tuning of said force/path abilities, i.e., of the first and the second range of operation, of the claimed boot.
In a further embodiment, if the boot is mounted on a plunge joint, at a maximal plunge radius r2 of said second fold goes ad infinitum, so that a progressively increasing axial force of said boot practically increases ad infinitum. Alternatively, one may say that the boot, thus prevents a disassembly of a joint on which the boot may be fixed. The aforesaid refers to the boot in accordance with the present disclosure in an extended state, where the shaft is pulled out as far as possible from the plunge joint casing. Such a boot will also show a first and a second range of operation A and B, respectively. Advantageously, the disassembly of the plunge joint will be hindered due to the maximal axial force acting on the boot in accordance with the present disclosure, and, thus, on a joint on which such a boot is mounted.
For example, the first fold of the fold region of the claimed boot is of convex shape. Further, e.g., the second fold of the fold region of the claimed boot is of concave shape. The geometrical design both of the first fold or the second fold may be further used for fine tuning the form stability of the boot in question. Especially, the second fold may have a radial, ellipsoidal, clotoidal, cosh-like or evolente-like geometry. For example, the second fold will have an essentially radial geometry. Further for example, the first fold will have an essential radial geometry.
The geometry of the first fold can be defined as essentially in the form of a semi-circle. Further, the second fold has, e.g., a radial geometry, and is embodied in an essentially semi-circle way. The latter especially holds if one would neglect the transition between the first fold and the second fold.
In a further embodiment, an angle β referring to the second transition region is in a range between approximately 0.5° to approximately 12°, more e.g., in a range between approximately 1° to approximately 10°, and most e.g., in a range between approximately 1.5° to approximately 7.5°. Said angle β is measured in accordance with the present disclosure between a straight defined by an inner surface of the second fastening region, and an inner surface of the conical part of the second transition region. The ratio of length of said conical part of the second transition region (L1) and a length of the second flange having a conical shape of the first transition region (L2), is in a range between 10:1 to 2:1, e.g., in a range of approximately 3:1 to approximately 4:1. The length L2 of the second flange of the first transition region as well as the length L1 of the conical part of the second transition region is measured in relation to the main axis of the boot, if viewed in a longitudinal section. Within the aforesaid definded ratios, it will be possible to avoid contact with the second fastening region, and especially the clamp, especially any clamp ear, being mounted in the second fastening region for mounting the boot on a shaft, and/or any kind of projections in the form of beads or earlike projections, being arranged on the outer surface of the second fastening region, at maximum articulation angles of a joint arrangement in which the boot in accordance with the present disclosure will be mounted. However, as the case may be, also ratios L1:L2 of 1:1 to 1:5 are within the scope of the present disclosure, especially if the boot will be used for propshafts.
In a further preferred embodiment of the present disclosure, a ratio of an inner radius r1 of the first fold and an inner radius r2 of the second fold is in a range of approximately 1:1 to approximately 1:40, e.g., in a range of approximately 1:2 to approximately 1:10. Said radius r1 and r2 are measured with respect to an inner contour of the first and second fold. If the geometrical design of the first and/or second fold will not be a radial design, making it easy to define radius r1 and r2, the aforesaid ratio will be defined by the maximum radius of curvature, for example if the first and/or second fold have an ellipsoidal or clotoidal geometry. Said ratio may also be used to fine tune the first and second range of operation of the boot claimed with respect to the form stability, especially as expressed by the retention force.
In a further preferred embodiment of the present disclosure, a ratio between the first minimal diameter D1 and a third diameter D3, defined by a straight, the straight being defined by an inner surface of the first fastening region of a first binder seat region of the claimed boot, is between approximately 65% to approximately 95% (app. 0.65:1 to app. 0.95:1), further preferred between approximately 72% to approximately 85%. If the boot is designed for ball-and-socket plunge joints, thus not having a trilobe contour, then the definition of the third diameter D3 is quite clear. If, however, the boot is designed with a trilobe contour, then it is assumed that the third diameter D3 is equal twice the distance between the main axis of the boot, if viewed in a longitudinal section, and the straight being defined by the inner surface by the first binder seat region in a non-trilobe part of the boot, where the distance is at its maximum. Also, third diameter D3 is defined in view of an unassembled boot.
The present disclosure further refers to a plunge joint with a rolling boot as defined above, especially a constant velocity joint, being construed as a trilobe joint or a ball joint. For example, the plunge joint can be a trilobe constant velocity joint, and the rolling boot can have a trilobe inner contour in the first fastening region, so that it is not necessary to use additionally an adapter. In such an arrangement, the first flange of the first transition region of the rolling boot, e.g., protrudes over an inner surface of the front edge of the joint casing, if viewed in a longitudinal section along the main axis of the boot, towards the interior of the boot. By this arrangement, a possible disassembly of the plunge joint will additionally be hindered. Further, such a protuberance of the bottom of the first flange of the first transition region over the inner surface of the front edge of a joint casing of said plunge joint will be observed in the un-lobe regions; if the plunge joint will be of trilobe contour.
Advantageously, a combination of the rolling boot in question with a plunge joint will lead to a kind of an automatical axial centering of a shaft to be inserted in such an arrangement.
Finally, the present disclosure also refers to a joint arrangement with at least one rolling boot in accordance with the present disclosure, with at least one plunge joint, and a shaft. For example, the at least one rolling boot can be mounted under tension. For example, the joint arrangement can comprise two plunge joints and at least one, e.g., two, rolling boots in accordance with the present disclosure. Further, the joint arrangement can comprise one plunge joint and one fixed joint, and at least one rolling boot. Exemplary joint arrangements are as follows:                a shaft with two plunge joints, e.g., tripode plunge joints, with two rolling boots in accordance with the present disclosure;        a shaft with two plunge joints, e.g., tripode plunge joints, with one rolling boot in accordance with the present disclosure, and one convolute (or diaphragm) boot or any other boot with decreased form stability, especially decreased axial retention force, compared to the rolling boot in accordance with the present disclosure;        a shaft with a fixed joint with a convolute (or diaphragm) boot and a plunge boot, e.g., a tripode plunge boot, with the rolling boot in accordance with the present disclosure, where the rolling boot is mounted under tension;        a shaft with two plunge joints, especially tripode plunge joints, and two rolling boots in accordance with the present disclosure, wherein both rolling boots are mounted under tension so that their overall length is shortened, compared to their length in an unmounted state;        a shaft as defined before, however, both rolling boots are mounted under tension in an expanded way, so that their mounted length is increased compared to their length in an unmounted state; and        a shaft with two plunge joints, especially tripode plunge joints, and with two rolling boots in accordance with the present disclosure, wherein both rolling boots are mounted under tension, namely one rolling boot with shortened length, and the other boot with increased length, compared to their length in an unmounted state;        
If a shaft with two plunge joints and two rolling boots in accordance with the present disclosure is provided, the boots not being mounted under tension, the axial force as well as the plunge path is distributed in an essentially equal way or in both rolling boots. If one rolling boot is mounted with shortened length, the other with increased length, one of the plunge joints will be urged in a retracted end position.
In the embodiment with two plunge joints, one rolling boot in accordance with the present disclosure and one convolute or diaphragm or any other boot with lesser form stability, especially lesser retention force, will lead to the plunge joint with the mounted convolute boot or any other boot with lesser form stability, compared to the rolling boot in question, mainly carrying out any movements of the shaft, whereas the other plunge joint with the mounted rolling boot in accordance with the present disclosure only provides for no or only little axial movements, thus acting similar to a fixed joint. The latter is due to the higher form stability of the rolling boot in question.
In the embodiment with the fixed joint with a convolute (or diaphragm) boot and the plunge joint with the rolling boot in accordance with the present disclosure, due to the axial force of the rolling boot in accordance with the present disclosure, the fixed joint will be pretightend in an axial way, so that the axial movement within the fixed joint will be compensated.
Other advantages and features of the disclosed subject matter will become apparent to one of skill in the art reading the following detailed description with reference to the drawings and illustrating various features by way of example only.